Content inventory tracking

[sacha-l]

PRs moving over to main for main-md:

• Rust basics: Review Rust basics #61
• Architecture: Architecture and Build process docs (and artifacts)  #46
• Deploy to testnet: Deploy to a test net #50
• ...

Node architecture (in "Fundamentals" section):

• Architecture: https://docs.substrate.io/v3/getting-started/architecture/
• Runtime: https://docs.substrate.io/v3/concepts/runtime/
• Executor: https://docs.substrate.io/v3/advanced/executor/
• Consensus: https://docs.substrate.io/v3/advanced/consensus/

Install:

• Install (Windows and Rust sections only): https://docs.substrate.io/v3/getting-started/installation/

Libraries (from "Build" section):

• Scale codec: https://docs.substrate.io/v3/advanced/scale-codec/
• Integrate sections (all): https://docs.substrate.io/v3/integration/

Tools (in "Reference" section):

• Tools sections (all): https://docs.substrate.io/v3/tools/

Design section:

• Smart contracts: https://docs.substrate.io/v3/runtime/smart-contracts/

Test:

• Benchmarking: https://docs.substrate.io/v3/runtime/benchmarking/
• Debugging: https://docs.substrate.io/v3/runtime/debugging/
• Testing: https://docs.substrate.io/v3/runtime/testing/
• Upgrades: https://docs.substrate.io/v3/runtime/upgrades/

Will use this issue to track other docs that get moved into the new structure. The goal is to empty our "old-docs-migration" folder.